Thanks for the replies. I was able to find a couple of places that sell belts that look like they could be adapted, but they start at about $40 apiece. The cost of a new external frame pack is about $100, so I didn't see that as a cost-effective choice. What I ended up doing was buying a couple of padded belts for an ALICE pack at about $10 apiece including shipping. I have yet to receive them, but pretty sure I will be able to adapt them. If worst comes to worst, one of the packs is a Kelty, so I suppose I could contact them.